1. Field of the Invention
The present invention relates to a technique for correcting a handshake in an image capturing apparatus, in particular, a handshake correcting technique of an image-adding-type.
2. Description of the Background Art
One of techniques for correcting a handshake in an image capturing apparatus is a handshake correcting technique of an image-adding-type.
In the handshake correcting technique of the image-adding-type, first, a plurality of images for handshake correction are successively captured by an image pickup device (such as a CCD sensor). Deviations of the subject position among the plurality of images are compensated, and corresponding pixels in the plurality of images in which the positional deviations are compensated are added, thereby generating a synthesized image (still image) obtained by synthesizing the plurality of images. According to the technique, by synthesizing a plurality of images by addition which is accompanied by suppression of movement of the subject by making exposure time per image relatively short to minimize movement of the subject during exposure, a sufficient exposure amount can be assured. As a result, a still image in which a handshake is corrected can be obtained.
One of techniques for shortening image process time in image synthesis process is a technique for synthesizing images by using characteristics of three color components (R (red) component, G (green) component, and B (blue) component) in images (refer to, for example, Japanese Patent Application Laid-Open No. 2002-112007). This publication discloses a technique for performing a synthesis process using mainly the G component.
However, the above positional deviation compensating technique is carried out by using an image (RGB image) obtained by a process (color interpolating process) for converting a Bayer matrix image to an RGB image. The “Bayer matrix image” is an image having the same pixel matrix as that of an image pickup device 5 having a Bayer matrix, and the “RGB image” is an image having R, G, and B components for each of pixels.
The number of RGB images after the converting process becomes three times as many as Bayer matrix images. There is, consequently, a problem such that a process load in the positional deviation compensation is heavy.
Even if efficiency is improved by applying the technique of the aforementioned publication to the handshake correcting technique, as long as the synthesis process is performed by using RGB images which are three times as many as Bayer matrix images, improvement in efficiency of image process is limited.